Stop MRSA!

Monday, July 31, 2006

CMAJ - July 18, 2006

The Canadian Medical Association Journal has just published an issue on MRSA - with a focus on community acquired MRSA (CA-MRSA). Click on the link above to read the articles, it's the July 18, 2006 issue.

Description: If you get sick with a bacterial infection this year, antibiotics from your doctor may not be a fool-proof answer. On Thursday, we discuss the serious medical problem of antibiotic resistance. Then, we explore the obstacles to new antibiotic development and what this means for public health. Then, a one-on-one interview with NPR Senior News Analyst Cokie Roberts. Guests: Dr. Jeff Stein, Sofinnova Ventures; Dr. Michael Chang, Optimer Pharmaceuticals; Cokie Roberts, NPR Senior News Analyst

If you're having trouble watching the video, try copying the following URL into your browser:http://video.google.ca/videoplay?docid=-8679672150030447262&q=mrsa&pr=goog-sl

Monday, July 10, 2006

Microbiology of MRSA

"MicrobiologyMethicillin resistance arises by acquisition of a staphylococcal cassette chromosome SCCmec, and is conferred by the mecA gene. Expression of this gene yields PBP2a, a penicillin binding protein with reduced affinity for β-lactam rings (the primary active-site of the β-lactam antibiotics).Some strains of S. aureus over-express β-lactamase and appear to be resistant to oxacillin and, rarely, methicillin despite being mecA-negative. They have slightly raised minimum inhibitory concentrations (MICs) and may thus be described as "minimally resistant". Other strains express modified PBPs (not PBP2) and exhibit varying degrees of β-lactam antibiotic resistance."

Tuesday, July 04, 2006

What is MRSA?

Here's a Wikipedia description on what MRSA is:

Methicillin-resistant Staphylococcus aureus (MRSA) is a specific strain of the Staphylococcus aureus bacterium that has developed antibiotic resistance to all penicillins, including methicillin and other narrow-spectrum β-lactamase-resistant penicillin antibiotics. MRSA was first discovered in the UK in 1961 and is now widespread, particularly in the hospital setting where it is commonly termed a superbug.MRSA may also be known as oxacillin-resistant Staphylococcus aureus (ORSA) and multiple-resistant Staphylococcus aureus, while non-methicillin resistant strains of S. aureus are sometimes called methicillin-susceptible Staphylococcus aureus (MSSA) if an explicit distinction must be made.

Monday, July 03, 2006

Epidemiology of MRSA

Up to 53 million people are thought to carry MRSA. Scientists estimate that around 2 billion people, some 25-30 percent of the world's population, have a form of the Staphylococcus aureus bacteria.

Because cystic fibrosis patients are often treated with multiple antibiotics in hospital settings, they are often colonised with MRSA, potentially increasing the rate of life-threatening MRSA pneumonia in this group. The risk of cross-colonisation has led to increased use of isolation protocols among these patients. In a hospital setting, patients who have received fluoroquinolones are more likely to become colonised with MRSA, this is probably because many circulating strains of MRSA are fluoroquinolone-resistant, which means that MRSA is able to colonise patients whose normal skin flora have been cleared of non-resistant Staph. aureus by fluoroquinolones.

In the US there are increasing reports of outbreaks of MRSA colonisation and infection through skin contact in locker rooms and gymnasiums, even among healthy populations. MRSA also is becoming a problem in paediatrics.

MRSA causes as many as 20% of Staphylococcus aureus infections in populations that use intravenous drugs. These out-of-hospital strains of MRSA, now designated as community-acquired, methicillin-resistant staph. aureus, or CA-MRSA, are not only difficult to treat but are especially virulent. CA-MRSA apparently did not evolve de novo in the community, but represents a hybrid between MRSA which escaped from the hospital environment and the once easily treatable community organisms. Most of the hybrid strains also acquired a virulence factor which makes their infections invade more aggressively, resulting in deep tissue infections following minor scrapes and cuts, and many cases of fatal pneumonia as well.

As of early 2005, the number of deaths in the United Kingdom attributed to MRSA has been estimated by various sources to lie in the area of 3000 per year. The staphylococcus bacteria accounts for almost half of all UK hospital infections.

During the summer of 2005, researchers in The Netherlands discovered that three pig farmers or their families were infected by MRSA bacteria that were also found on their pigs. Researchers from Radboud University Nijmegen are now investigating how widespread the MRSA bacteria is in pigs, and whether it will become characterised among the zoonoses.

Recently, it has been observed that MRSA can replicate inside of Acanthamoeba, increasing MRSA numbers 1000-fold. Since Acanthamoeba can form cysts easily picked up by air currents, these organisms can spread MRSA via airborne routes. Hence, control of Acanthamoeba in the clinical environment may be advisable.